With sites like AirBnB and Craigslist, it's easier than ever to turn your homes into a full-fledged budget hostel—and line your pockets with extra cash in the meantime.

But as with any side gig that brings in extra income, you can bet the IRS will mind if you fail to mention your new role as small-time innkeeper. AirBnB helps hosts by prompting them with proper tax forms each year, but the average joe renting out his basement on the side might not know when he's crossed into taxable territory.

If you want to skirt around taxes: “Rental income is usually taxable under the Federal tax laws. But there is an exception if you rent out a home that you use as a home and the home is rented less than 15 days during the year. The exception is that rental income and rental expenses are not reported on your return at all. This allows a person to rent out his or her home for a short period of time with no tax consequences.”

If you're not renting out your prime residence: “In addition to renting the home 14 or fewer days during the year, you must use the home for personal purposes more than the greater of 14 days or 10% of the total days it is rented to others at a fair rental price. This is no problem if you are temporarily renting out one spare room in a home that you live in. But for second homes or vacation homes, you need to keep track of your days.”